Molecular cloning, genomic organization, and mapping of PRKAG2, a heart abundant gamma(2) subunit of 5 '-AMP-activated protein kinase, to human chromosome 7q36

5'-AMP-activated protein kinase (AMPK) acts as a major regulator of cellula r ATP levels and protects cells against stresses that cause ATP depletion. AMPK is a protein heterotrimer composed of a catalytic alpha subunit and tw o regulatory subunits, beta and gamma. In the present study, a homologue of the AMPK gamma (1)-subunit cDNA with an open reading frame encoding 328 am ino acids was identified. The putative protein sequence is about 76% identi cal to the 331-amino-acid gamma (1) subunit and also has four consecutive c ystathionine-beta -synthase (CBS) domains, a characteristic structure of AM PK gamma subunits from various species. This cDNA (tentatively termed PRKAG 2-b) is identical to a recently reported cDNA (tentatively termed PRKAG2-a) of human AMPK gamma subunits except in their 5'-end regions, suggesting th at these two cDNAs are two different transcripts of the same gene. To deter mine the expression pattern of the gene, two probes, one from the 3'-UTR of PRKAG2-b and the other from the 5'-unique region of PRKAG2-a, were used to hybridize MTN membranes. Three transcripts (3.8, 3.0, and 2.4 kb) were obs erved when the first probe was used, whereas only 3.8- and 3.0-kb transcrip ts were seen when the second probe was used. Thus, the PRKAG2-b corresponde d to the 2.4-kb transcript, which is ubiquitously expressed except in liver and thymus. The highest level was detected in heart, while abundant expres sion also existed in placenta and testis. The expression pattern of PRKAG2- b is completely different from those of PRKAG2-a and PRKAG1, whose expressi on patterns were also determined in the current study. The PRKAG2 gene was located to human chromosome 7q36 between markers D7S2439 and D7S2462 by rad iation hybrid mapping. The genomic organization of PRKAG2-b was identified by comparing its cDNA sequence with two genomic sequences AC006358 and AC00 6966, which showed that PRKAG2-b spanned an similar to 80-kb region and was composed of 12 exons. (C) 2000 Academic Press.